TRENTON, N.J.  Environmentalists on Tuesday will urge the governors of New Jersey and Delaware to enforce strong new protections for a migratory shorebird threatened with extinction.

Eight conservation groups in the two states are rallying on behalf of the red knot, a species that migrates from South America to the Arctic to breed each spring. The birds' principal stopover is New Jersey and Delaware, where they spend weeks fattening up on horseshoe crab eggs before continuing their 6,500-mile journey.

The environmental coalition will ask the states to ban horseshoe crab harvests for the rest of the year and to keep beaches hosting red knots closed until the birds leave, said Jeff Tittel, executive director of the New Jersey Sierra Club.

"The measures we have in place now are not working," said Tittel. "Since the numbers are so bad this year, we have to do more."

The number of red knots has become precipitously low, after declining for years. A recent survey of red knots in South America set the population at 17,653, down from already low counts of 51,255 in 2000 and 27,242 in 2002. Ten years earlier, scientists estimated the red knot population at 100,000.

Eric Stiles, vice president for conservation and stewardship with the New Jersey Audubon Society, said the study suggests that if nothing is done, the red knot population will be at or near extinction by 2011.

New Jersey and Delaware officials have been working together in recent days to determine what, if any, additional steps the two states should take, New Jersey Department of Environmental Protection Commissioner Bradley Campbell said Monday.

"We're very alarmed by the limited data we've seen so far showing precipitous declines in the red knot population and horseshoe crab eggs they depend on for survival," Campbell said. "The difficulty is, we're working with a very limited data set. It's a tough call given the impact on fishermen whether additional restrictions are appropriate now."

Officials in Delaware and New Jersey banned harvesting of horseshoe crabs from May 1 through June 7, the peak of the crab spawning season and shorebird migration. That action came on top of significant reductions in harvests by Delaware and other states on orders from the Atlantic States Marine Fisheries Commission.

Despite the ban, Tittel said horseshoe crab eggs on the beaches are at record low, "which means the red knots who did make it here may not have enough to eat to put on body fat to make it up to the Arctic to breed."

If the harvesting ban is lifted Tuesday as scheduled, baymen will be permitted to take horseshoe crabs two days a week.

To further help the birds, conservation officers patrolled some beaches to keep people and dogs away. The beach bans also were due to be lifted Tuesday.

Efforts are under way to have the bird listed on the national endangered species list. It is already listed as a threatened species in New Jersey.